A hierarchically porous CoS2-NiS2 heterojunction for high-performance lithium sulfur batteries

Abstract

The commercial development of lithium-sulfur batteries (LSBs) has been significantly hindered by the “shuttle effect” and the slow redox kinetics of lithium polysulfides (LiPSs). To solve these problems, researchers have designed a variety of catalysts for the conversion of LiPSs. However, the multi-step lithium polysulfide conversion process is difficult to be effectively solved by a single-function catalyst. In this study, a novel hollow nanocage composite CoS₂/NiS₂ with heterogeneous interfaces (CoS₂-NiS₂) is designed to dual modify the cathode host and separator. These CoS₂-NiS₂ heterojunctions can enhance the trapping ability of LiPSs and improve the wettability, thereby mitigating the shuttling of LiPSs. Besides, the CoS₂-NiS₂ heterogeneous interface exhibits a strong internal electric field, which effectively enhances the electronic conductivity of the composites. Moreover, this strong electric field at the CoS₂-NiS₂ heterojunctions offers excellent catalytic ability for sulfur reduction so that can remarkably promote the conversion of LiPSs. Due to these multi-functional characteristics, the CoS₂-NiS₂ nano-composite demonstrates excellent adsorption and catalytic properties. The as-obtained battery achieves a high initial specific capacity of 1037.4 mAh g⁻¹ and a low decay rate of 0.047 % per-cycle. This study offers a comprehensive understanding of interfacial catalytic mechanisms and their impact on sulfur reaction kinetics, particularly for binary metallic-compounds heterojunctions.